Fiber reinforced composite structures are present in many products ranging from simple containers to vital structural components of jet aircraft. The benefits of using fiber reinforced composite structures in the construction of these many products results from its three main attributes: minimal weight, high strength and flexibility of design through laminated construction. Typically, fiber reinforced composite structures have been constructed using fiber reinforcing members (fabrics) having either a planar woven structure or a three dimensional woven structure.
Fabrics having a planar woven structure are often layered, forming laminates. Laminated construction permits fiber reinforced composite structures to be used in areas where a tapered or curved surface is required, since each layer of the laminate can be cut independently of the other layers.
A problem with the laminated construction is that the through-tee-thickness reinforcement provided by the fabric is at a minimum. One technique that has been tested for improving the through-the-thickness reinforcement of a composite structure has been to stitch the layers of the laminate together. However, the stitching results in damage to the fabric layers.
Fabrics having a three dimensional woven structure provide a much greater through-the-thickness reinforcement than the laminates formed by the layering of fabrics having a planar woven structure. The through-the-thickness reinforcement of these three dimensional woven fabrics is substantially reduced if the fabric is cut in order to make a taper or a curve.
Other fabrics, that have not been used in the fiber reinforced composite structure field, are similar in appearance to fabric constructions which are useful in the present invention. For example, U.S. Pat. No. 2,424,771 (Preneta) describes a fabric having upstanding ribs. The purpose of this ribbed design is to provide a longer wearing fabric with an improved appearance.
Were such ribbed fabric used as a laminate in a fiber reinforced composite structure it is doubtful that the through-the-thickness reinforcement would be improved since the ribbing does not extend significantly beyond the face of the fabric to effectuate a reinforcing action between the fabric and its colaminate.
U.S. Pat. No. 3,177,904 (Siverson) describes a fabric designed to provide a superior gripping surface for a conveyor belt. Applicant believes that the outstanding loops that provide this superior gripping surface would not enhance the through-the-thickness reinforcement of a fiber reinforced composite structure, since the round shape and the wide spacing of the loops would not effectuate a snug nesting of the lamina. The Siverson fabric does not suggest that the loops be altered in either shape or spacing. To do so may inhibit their intended purpose as a gripping surface for a conveyor belt.